Optical computing is recognized as an emerging technology. Its continued maturation depends heavily on the availability of a wide range of logic devices and, more specifically, optical devices performing combinatorial logic functions. While the range of combinatorial logic functions such as AND, OR and NOT is important in the first instance, it is almost equally important to provide cascadability, logic level restoration, phase insensitivity, speed and input/output isolation. An additional consideration, though not presently decided upon, may be a need for an all-optical device.
A symmetric self electrooptic effect device commonly known as the S-SEED is the only known device to achieve many of the attributes shown above while affording a means for performing combinatorial logic functions. See, for example, U.S. patent application Ser. No. 341,524 and an article by A. Lentine et al. appearing at Appl. Phys. Lett., Vol. 52, No. 7, pp. 1419-21 (1988). The S-SEED is an electrooptic device owing to the fact that it is electrically biased with a pair or semiconductor quantum well diodes interconnected to achieve a proper degree of electrical feedback so that impinging optical signals are correctly processed. As such, the S-SEED does not meet the potential criterion for an all-optical device. Moreover, while the S-SEED does provide gain, it does so in a time-sequential manner. In this mode of operation, optical data signals impinge on the device during a first time instant for combinatorial logic processing and a resultant signal, which represents the result of performing the logic function on the optical data signals, is read out of the S-SEED by a higher power optical clock signal during a later time instant. Accordingly, the S-SEED lacks the capability for real-time operation when providing time-sequential gain for cascadability.